Insert molding is a manufacturing process where a preformed piece of metal or other material is placed inside of a plastic injection mold, allowing the molten thermoplastic to be injected around it. This results in a single strongly bonded integrated assembly with the insert or inserts encased within the new plastic, reducing post-molding assembly time and costs. Inserts can be made of metal, another plastic, ceramic or any substance that will hold up to the injection process.
The insert is positioned in the injection mold with its intended holes, and the plastic is molded around it. This can be done with a single shot or multiple shots, depending on the part and production needs. The insert can also be removed and replaced if needed, making this a versatile and adaptable method of creating a molded part with multiple components.
In addition to the cost savings, insert molding allows for a greater degree of design flexibility. This can be especially helpful in a wide variety of industries, such as automotive, medical and electronics. For example, many electrical and computer parts are overmolded with plastic or rubber to protect sensitive inner components. Medical devices like defibrillators often have wires and coils encased in plastic using insert molding as well. This both reduces the risk of damage and makes them easier to sterilize for use.
Regardless of the industry, insert molding can save time and money by eliminating separate post-molding assembly processes. This can significantly lower a product’s time to market. Additionally, the ability to integrate features that cannot be manufactured with plastic alone can lead to stronger, more reliable products. For example, a stainless steel insert can be added to strengthen fastening areas or prevent creep.
When deciding on whether to employ manual or automated loading, it is important to consider the volume of production and the overall unit price of each component. For smaller volumes, manual loading is typically more cost effective. However, for higher volume production, robotic systems can be more efficient and reduce unit costs by allowing an injection molding machine to run continuously without the need for a full-time operator.
A thorough understanding of the insert and injection molding processes is critical to ensuring that the process will be successful. It is important to understand the physical limitations of your injection molding machine, the dimensions and tolerances of your inserts and how much pressure will be applied to them during the injection process. Additionally, a solid design of the product will allow for proper positioning and alignment of the inserts in order to get the most out of the injection molding process.
It is also critical to pay close attention to the materials used in the inserts and the injection molding process, as these will impact the quality of your final product. In general, inserts should be made of a tougher material than the plastic in order to hold up to the injection molding process. For example, copper and brass are excellent choices for threaded inserts, while perforated plate type inserts can be utilized when a higher strength than brass provides is required (although this can increase overall production cost). Inserts should also be designed to avoid movement during the injection molding process, and the mold depth should be large enough to accommodate them.